diff -r d943089af1c6 Lib/posixpath.py
--- a/Lib/posixpath.py	Mon Jun 30 04:04:52 2014 +0300
+++ b/Lib/posixpath.py	Sun Jun 29 23:10:30 2014 -0400
@@ -34,6 +34,7 @@
 defpath = ':/bin:/usr/bin'
 altsep = None
 devnull = '/dev/null'
+mixed_string_binary_error = "Can't mix strings and bytes in path components."
 
 def _get_sep(path):
     if isinstance(path, bytes):
@@ -87,8 +88,7 @@
                           for s in (a, ) + p)
         if valid_types:
             # Must have a mixture of text and binary data
-            raise TypeError("Can't mix strings and bytes in path "
-                            "components.") from None
+            raise TypeError(mixed_string_binary_error) from None
         raise
     return path
 
@@ -447,9 +447,15 @@
     if start is None:
         start = curdir
 
-    start_list = [x for x in abspath(start).split(sep) if x]
-    path_list = [x for x in abspath(path).split(sep) if x]
-
+    try:
+        start_list = [x for x in abspath(start).split(sep) if x]
+        path_list = [x for x in abspath(path).split(sep) if x]
+    except TypeError as e:
+        valid_types = all(isinstance(s, (str, bytes, bytearray))
+                          for s in [start, path])
+        if valid_types:
+            raise TypeError(mixed_string_binary_error) from None
+        raise
     # Work out how much of the filepath is shared by start and path.
     i = len(commonprefix([start_list, path_list]))